On the importance of accurate stampmanship

A pet peeve of mine: when we stamp due dates here at the Circ Desk, we stamp them on little slips of paper with four panels on them. As each panel has ample room for our stamps, theoretically speaking one should be able to circulate a book four times before having to add another due date slip (they have adhesive backings so we just slap them on top of the old slip). Unfortunately sometimes people get a little sloppy with their stamping and end up taking up two panels of space, which although annoying isn't the end of the world; but every once in a while some dingbat stamps the blank slip right smack in the middle, making it virtually impossible to get another due date on there.

In the name of Melvil Dewey, I ask why? Is it bad aim on the part of the stamper, or is there a hint of malicious intent here? Either way it's a royal pain in the ass.